The present invention relates to a probe or sampling tube which can be introduced into a reaction container for detecting the operating condition of a solid, liquid or gaseous medium in the interior of the container, which medium is possibly under pressure and/or at a high temperature. At its lower end, the probe tube has a measuring sensor which represents the end of measuring lines which are passed through the hollow space inside the tube and which are taken out at the upper end thereof. The probe tube is usually provided with a sealing means which sealingly surrounds the measuring lines so that the medium which is to be subjected to the operation of determining the operating condition thereof cannot escape from the interior of the container by way of the probe tube. Probes of that kind operate on different measuring principles, for example with electrical conductors or optical fibres.
Probe tubes of the above-indicated kind are used for example to detect the operating condition of bulk materials, in the nature of solid bodies, in a container, for example the generation of gases such as carbon dioxide (CO.sub.2) or methane (CH.sub.4) in a reactor containing lignite or brown coal dust, or other containers. Containers of that kind are usually not under pressure and the temperature in the interior of the containers is not substantially above ambient temperature.
However, the operating condition within gasification reactors of the high temperature Winkler (HTW) kind or for the hydrogenating gasification of coal (HGC) can also be measured with probe tubes, by detecting the nature and amount of the gases of solid-like coal particles which are gasified in the fluidized bed. In that case, temperatures and pressures are considerably above the ambient values. Probe tubes of the above-indicated kind are also used in reaction vessels in the hydrogenating liquefaction of carbonaceous material; in that case, the temperatures are in the range of from 300.degree. C. to 500.degree. C. while the pressures are from 100 to 500 bar.
The condition of the medium in the interior of the container goes from highly fluid to pasty consistency, but at the same time there are also gaseous conditions.
Measuring probes which are introduced into a reaction container of the kind last mentioned, during operation of the arrangement, are used for example to obtain information about the fluid-dynamic conditions, that is to say, the size and speed of the bubbles of gases which are introduced into or produced in the container. In addition, probes are intended to give information about the proportion of the gaseous phase in the liquid medium and the distribution in respect of size of the bubbles.
For that purpose, two measuring lines, for example optical fibres, are passed in parallel relationship with each other through the length of the probe tube and brought together at its lower end to a measuring sensor, while at the upper end of the probe tube which projects out of the reaction container, the measuring lines are taken out of the tube and connected to the appropriate measuring instruments. Laser light for example is passed through the first optical fibre referred to above, and taken back through the other optical fibre. Gas bubbles which impinge onto the measuring sensor reflect a part of the incident laser light so that it can be detected by way of the measuring line which is taken out of the probe tube. The frequency and intensity of the reflection phenomena are for example a measurement in respect of the gaseous phase which is dissolved in the liquid medium.
A measuring sensor of the above-described kind is highly sensitive and must be protected from damage and other mechanical influences, for example pressure forces. It is also necessary for the location at which the measuring lines are taken through the probe tube to be so gas-tight that the medium in the reaction container cannot escape therefrom. Casting or sealing materials have been used for that purpose, the space inside the probe tube being filled with such material so that the measuring lines are embedded in the material on all sides, while the casting material provides the necessary sealing action. It has been found however that known casting or sealing materials do not comply with all requirements in regard to the sealing action, such requirements arising out of the reaction conditions within the container. Thus for example it is possible to use a two-component adhesive to produce a sealing material which, although resistant to temperature, is not adequately pressure-resistant and gas-tight. There is no casting or sealing material which simultaneously complies with all three conditions, namely high level of resistance to temperature, for example above 300.degree. C., high resistance to pressure, for example above 100 bars, and a high degree of gas-tightness, in particular in relation to low-molecular gases such as hydrogen (H.sub.2) or helium (He).
Therefore, that frequently results in a one-sided pressure load and increased temperature loading on the measuring sensor, with the result that the measuring sensor is pushed into the interior of the probe tube and becomes pervious to gas. That means that such measuring probes become useless after a short period of operation.
Consequently, derived from those disadvantages is the problem of the present invention, of so designing measuring probes that they are protected from the temperatures and pressures occurring in the interior of the reaction container.